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that prevents the dredge spoils from migrating or leaching back into the 

 environment. They are usually bermed and are either lined with plastic or 

 clay soils. A CDF can be located either on the shoreline or upland. A CDF 

 requires long-term monitoring of the surrounding soil, surface water, and 

 groundwater to ensure that contaminants are not leaching. Another problem 

 with a CDF is placement on a shoreline, which takes away fish habitat and 

 foraging grounds for shorebirds and waterfowl. The cost of building a CDF is 

 approximately $1 million per acre. 



Capping is an alternative for material that may be unsuitable for unconfined 

 open-water disposal because of potential contaminant effects on benthic 

 organisms. Capping is defined as the controlled, accurate placement of 

 contaminated dredge material at an open-water disposal site, followed by a 

 covering or cap of clean isolating material. Capping contaminated dredge 

 material with a layer of clean soil is considered an appropriate containment 

 control measure to prevent dredge spoils from coming into contact with marine 

 organisms. Capping requires long-term monitoring because of potential effects 

 on benthic toxicity or bioaccumulation if the material is disturbed. 

 Long-term monitoring concerns include whether the cap remains in place or 

 erodes and whether the contaminants remain within the clean cover material or 

 are being transported to the sediment surface layer or water column. Capping 

 is not usually a beneficial option because of long-term monitoring and the 

 possible need to further remediate the dredge spoils at a later time. The 

 cost of capping is usually $3.00 to $6.00 per cubic yard. 



Chemical fixation/stabilization is a process performed in a designated 

 processing unit by adding a pre-determined reagent formulation to the dredge 

 material. Through a series of chemical reactions, the contaminated dredge 

 material becomes encapsulated, rendering the dredge spoils safe, 

 non-polluting, non-leaching, and chemically stable. Chemical fixation will 

 chemically change the metal oxide compounds to metal meta-sil icate compounds, 

 which render the material non-soluble in water. Following 

 fixation/stabilization, material may be placed into a municipal landfill. 

 However, landfill ing materials is not usually an option because of long-term 

 future liability associated with landfill disposal. The cost of chemical 

 fixation is $60.00 to $75.00 per cubic yard. 



Screening/size separation of dredge material is a process utilizing standard 

 equipment, most of which has been used for decades in the mining business. 

 Gross oversize materials are separated from the dredged material using 

 mechanical screening techniques, while the coarse and fine grain materials are 

 separated by the use of hydrocyclones. Hydrocyclones are used to separate 

 coarse grain sands from fine grain materials by using screens of different 

 sizes which spin and shake the material while directing each size fraction to 

 different flow paths. Gravity separators are also used to separate coarse 

 grain from fine grain fractions. Coarse grain materials, usually sand, are 

 separated from contaminants; thereby, allowing the resulting sand material to 

 be used for ocean disposal or beach replenishment. The finer grained 

 fractions contain the contaminants. Disposal options vary depending on the 

 contaminants contained in the material. The cost for size screening/size 

 separation is $35.00 to $50.00 per cubic yard. 



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